Method of manufacturing ceramic layered product

ABSTRACT

In order to manufacture a ceramic layered product for manufacturing a multilayer ceramic capacitor, a plurality of reels (23) are prepared, which are wound with a plurality of types of elongated mother ceramic sheets (12), each having a plurality of electrode patterns (14) and a plurality of registration marks (15) distributed along its longitudinal direction. The mother ceramic sheets (12) are drawn out from the respective reels (23) onto related sheet cutting stages (25). Regions including the electrode patterns (14) are punched from respective ones of the mother ceramic sheets (12) provided on a selected sheet cutting stage (25) by a cutting head (52) whose periphery is enclosed with a cutting edge (51) on the basis of the registration marks (15). Then the ceramic sheets (35) punched out from the mother sheet by the cutting head (52) are carried to a stacking jig (34) by the cutting head (52) and stacked with each other on the stacking jig (34).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of and an apparatus formanufacturing a ceramic layered product.

2. Description of the Background Art

In order to manufacture a multilayer ceramic electronic component suchas a multilayer ceramic capacitor, a multilayer inductor or a multilayercircuit board, for example, raw ceramic sheets are stacked with eachother to prepare a ceramic layered product. For example, a ceramiclayered product for a multilayer ceramic capacitor has generally beenobtained by the following method or apparatus:

As shown in FIG. 10, a previously prepared mother ceramic sheet is drawnout from a sheet drawing station 1 to an electrode printing/cuttingstation 2, where the mother ceramic sheet is punched while electrodesare simultaneously printed on the ceramic sheets, which are punched outfrom the mother ceramic sheet. After the punching step, the motherceramic sheet is discharged as a scrap sheet, while the ceramic sheetsprovided with the electrodes are dried in a drying station 3, andthereafter stored in a sheet storage station 4.

The stored ceramic sheets are selected to provide the characteristics,such as capacitance, required for the multilayer ceramic capacitor to beobtained. They are stacked and aligned with each other on the basis oftheir end surfaces. Then the aligned ceramic sheets are inserted in astacking jig, and subjected to press working.

However, the aforementioned system has the following problems:

(1) A large space is required in order to store the punched ceramicsheets.

(2) Since the electrodes are printed simultaneously with the cutting ofthe ceramic sheets through a mechanical positioning mechanism, electrodepositions are not much dispersed in the same type of electrode patterns.When the electrode patterns are exchanged, however, the electrodepositions are apt to be dispersed between the different types ofelectrode patterns.

(3) When the electrode patterns are exchanged, it takes much time tolocate the electrode patterns on cutting positions.

(4) Since the ceramic sheets are aligned with each other on the basis oftheir end surfaces, the electrode positions of the aligned ceramicsheets still remain dispersed resulting from the problem described abovein paragraph (2), to cause dispersion the capacitances of the multilayerceramic capacitors obtained by this method. Further, the electrodepositions may also be dispersed by the aligning operation itself.

(5) If static electricity is generated between the ceramic sheets, or ifthe ceramic sheets have small thicknesses, it is difficult to align theceramic sheets.

(6) The aligned ceramic sheets may be displaced from each other whenthey are inserted in the stacking jig.

Due to such problems of the system shown in FIG. 10, it has beendifficult to stack the ceramic sheets with high accuracy.

In order to solve the problems in relation to handling the ceramicsheets in the aforementioned system, the applicant has proposed thefollowing system, which is not yet known in the art:

As shown in FIG. 11, a sheet drawing station 5 is continuously coupledthrough an electrode printing station 6, a drying station 7 and acutting/stacking station 8 to a scrap sheet winding station 9. A ceramiclayered product is taken out from the cutting/stacking station 8. Thefeature of this system resides in that the electrode printing station 6and the drying station 7 are provided in front of the cutting/stackingstation 8.

However, the aforementioned system has the following problems:

(1) This system can merely manufacture the same type of ceramic layeredproducts in relation to electrode patterns.

(2) When the items are switched, it takes much time for setup operationssuch as exchange of print patterns, exchange of sheets and the like.

(3) The system requires leader and end sheets extending beyond thelength of the apparatus or the production line, to cause reduction ofthe material yield.

(4) Due to the continuous steps, complicated operations are required fordealing with possible defective prints and returning to the normaloperation.

(5) In order to obtain a ceramic layered product for a multilayerceramic capacitor, in particular, it is necessary to frequently driveand stop a printer in order to continuously obtain both ceramic sheetsprovided with electrodes and those provided with no such electrodes.Thus, printing accuracy is deteriorated due to irregular printingconditions.

(6) This system is unsuitable for multi-item dab production because ofthe problems mentioned above in paragraphs (1) to (3), although the sameis suitable for mass production with small setup changes.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a methodof and an apparatus for manufacturing a ceramic layered product, whichcan stack ceramic sheets with high accuracy and advantageously be usedin multi-item dab production.

The inventive method of manufacturing a ceramic layered productcomprises the steps of:

preparing a plurality of reels wound with a plurality of types ofelongated mother ceramic sheets each having a plurality of electrodepatterns, and a plurality of registration marks having constantpositional relations to the electrode patterns, distributed along itslongitudinal direction,

drawing out the mother ceramic sheets from the plurality of reels ontorelated sheet cutting stages,

punching a region including at least one of the electrode patterns fromone of the mother ceramic sheets, on a selected one of the sheet cuttingstages, on the basis of the registration marks, employing a cutting headwhose periphery is enclosed with a cutting edge, and

carrying the ceramic sheets, which have been punched out from the motherceramic sheet by the cutting head, to a stacking jig, the ceramic sheetsbeing carried by the cutting head, and stacking the ceramic sheets onthe stacking jig.

The inventive apparatus for manufacturing a ceramic layered productcomprises:

a reel stand for setting holding a plurality of reels wound with aplurality of types of mother ceramic sheets each having a plurality ofelectrode patterns, and a plurality of registration marks havingconstant positional relations to the electrode patterns, distributedalong its longitudinal direction, the reels being parallel with eachother,

a plurality of sheet cutting stages for positioning the mother ceramicsheets drawn out from the plurality of reels respectively,

a stacking jig for stacking ceramic sheets obtained by punching a regionincluding at least one of the electrode patterns from one of the motherceramic sheets thereon,

an optical sensor for detecting positions of the registration marks ofthe mother ceramic sheets provided on the sheet cutting stages, and

a cutting head, being movable between the plurality of sheet cuttingstages and the stacking jig and having a periphery enclosed with acutting edge for punching the regions of the mother ceramic sheetsincluding the electrode patterns, which is adapted to carry ceramicsheets punched out from the mother ceramic sheets.

According to the present invention, the mother ceramic sheets providedwith the electrode patterns are first taken up on the reels. Thus, it ispossible to store the mother ceramic sheets with the electrode patternswound on the reels, and the step of forming the electrode patterns byprinting etc. can be separated from the later sheet cutting and stackingsteps.

In the sheet cutting and stacking steps, a plurality of types of reelsare set to punch out an arbitrary number of ceramic sheets from anarbitrary one of the mother ceramic sheets wound on the reels inaccordance with a prescribed program, and then the ceramic sheets arestacked with each other.

In the sheet cutting step, the positions where the mother ceramic sheetsare to be punched are corrected on the basis of the registration marks,which are simultaneously printed with the electrode patterns in constantpositional relations thereto, in order to cut the ceramic sheets.

After the mother ceramic sheet is punched by the cutting head, theceramic sheets are directly carried by the cutting head and stacked witheach other on the stacking jig.

According to the present invention, the mother ceramic sheets providedwith the electrode patterns are first taken up on the reels so that thesame can be separated from the later sheet cutting and stacking steps.Thus, it is possible to prepare the mother ceramic sheets provided withthe electrode patterns in a mass even for multi-item dab production,thereby improving the material yield.

Since the mother ceramic sheets are stored wound on the reels, theceramic sheets can be easily handled, thereby reducing the time requiredfor exchanging the mother ceramic sheets in order to switch the items,etc.

Further, it is possible to stack ceramic sheets having different typesof electrode patterns with each other in arbitrary order by setting aplurality of reels wound with a respective plurality of types of motherceramic sheets. In addition, it is possible to set reels and motherceramic sheets to be used in manufacturing a subsequent product lot onnonused reel stand and sheet cutting stages, so that the setup time canbe reduced to advantageously cope with multi-item dab production.

Since the ceramic sheets are punched out on the basis of theregistration marks, which are formed with constant positional relationsto the electrode patterns, and then stacked with each other, it ispossible to stack ceramic sheets of a type generating static electricitytherebetween or ceramic sheets having extremely small thicknesses,unlike with to the conventional system of aligning the ceramic sheetswith each other on the basis of their end surfaces. When the electrodepatterns and the registration marks are simultaneously formed byprinting, print patterns therefor may simply be adjusted so that theregistration marks come into the visual field of an optical sensor suchas a CCD camera. Thus, the time for exchanging the print patterns isreduced.

The ceramic sheets are punched out from the mother ceramic sheet by thecutting head on the basis of the registration marks, directly carried bythe cutting head onto the stacking jig, and stacked with each other onthe stacking jig. Therefore, it is possible to prevent errors which maybe caused before the cut ceramic sheets are inserted in the stackingjig.

Thus, the ceramic sheets can be stacked with each other with highaccuracy, to enable manufacturing of a high capacity multilayer ceramiccapacitor, for example.

If defects are caused in the electrode patterns by errors in printing,the mother ceramic sheets may simply be moved to skip such defectivepatterns, in order to readily cope with such errors.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an exemplary production line formanufacturing a ceramic layered product, including an embodiment of thepresent invention;

FIG. 2 is a plan view showing a part of a mother ceramic sheet 12;

FIG. 3 is a perspective view showing a cutting/stacking device 22;

FIG. 4 is a sectional view showing a structure employed for a sheetcutting stage 25;

FIG. 5 is a perspective view showing a stacking jig 34;

FIG. 6 is a front elevational view illustrating a conveyor 36 and astructure related thereto;

FIGS. 7, 8 and 9 are front elevational views for illustrating operationsof a cutting head 52 and CCD cameras 49 and 50;

FIG. 10 is a block diagram showing a conventional production line formanufacturing a ceramic layered product, which is of interest to thepresent invention; and

FIG. 11 is a block diagram showing a production line for manufacturing aceramic layered product, proposed by the applicant, which is not yetknown in the art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 schematically illustrates an exemplary production line formanufacturing a multilayer ceramic capacitor, which employs anembodiment of the method of the present invention.

Referring to FIG. 1, a long mother ceramic sheet, which is prepared byany well-known method, is set in a sheet drawing station 10, and drawnout therefrom toward an electrode printing station 11. The motherceramic sheet may be prepared from a ceramic green sheet which is backedby an appropriate reinforcing sheet, or from an independent ceramicgreen sheet.

In the electrode printing station 11, a plurality of electrode patterns14, each including a plurality of electrodes 13, are printed on themother ceramic sheet 12 as shown in FIG. 2. The plurality of electrodepatterns 14 are distributed along the longitudinal direction of themother ceramic sheet 12. Simultaneously with such printing of theelectrode patterns 14, registration marks 15 having constant positionalrelations to the electrode patterns 14 are printed on the mother ceramicsheet 12.

The electrode patterns 14 and the registration marks 15 printed in theaforementioned manner are thereafter dried in a drying station 16.

Then, the mother ceramic sheet is wound on a reel in a sheet windingstation 17.

In such a manner, a plurality of reels, which are wound with arespective plurality of types of mother ceramic sheets, are prepared asneeded. The reels wound with the mother ceramic sheets are stored in asheet storage station 18.

Then, the reels containing desired types of mother ceramic sheets areselected from the plurality of reels which are stored in the sheetstorage station 18, and set in a cutting/stacking station 19. In thecutting/stacking station 19, regions 20 including the electrode patterns14 are punched from each mother ceramic sheet 12 as shown in FIG. 2, andthen the ceramic sheets punched out from the mother ceramic sheet 12 arestacked with each other.

A ceramic layered product, which is formed by the stacked ceramicsheets, is then pressed in a pressing station 21.

The cutting/stacking station 19 will now be described in detail withreference to FIGS. 3 to 9.

FIG. 3 is a perspective view showing the overall structure of acutting/stacking device 22 which is employed in the cutting/stackingstation 19.

The cutting/stacking device 22 comprises a reel stand 24 for setting sixreels 23, for example, which are selected from the plurality of reelscontaining different types of mother ceramic sheets stored in the sheetstorage station 18 shown in FIG. 1, oriented parallel with each other.While FIG. 3 illustrates the reels 23 as containers in the form ofequilateral square poles, the reels are rotatably stored within suchcontainers in practice, so that the mother ceramic sheets 12 are drawnout from openings provided in parts of the containers.

The mother ceramic sheets 12 drawn out from the reels 23 are positionedon sheet cutting stages 25 respectively. FIG. 4 shows the structure ofeach sheet cutting stage 25.

Referring to FIG. 4, each sheet cutting stage 25 includes a beltconveyor mechanism which is formed by a mesh belt 26. The mesh belt 26is extended along three rollers 27, 28 and is 29, and driven to move themother ceramic sheet 12 along the arrow 30. When the mother ceramicsheet 12 is on a horizontally directed path, a suction device 31attracts the mother ceramic sheet 12 through the mesh belt 26, therebypositioning the sheet. This sheet cutting stage 25 is adapted to punchthe regions 20 (FIG. 2) of the mother ceramic sheet 12 including theelectrode patterns 14 as hereinafter described in detail. A resultingscrap sheet 32 is cut into pieces by a cutter 33 every feed.

Referring again to FIG. 3, stacking jigs 34 are arranged in the vicinityof the sheet cutting stages 25. FIG. 5 is an enlarged view showing astacking jig 34, which is adapted to stack a prescribed number ofceramic sheets 35 obtained by punching out the regions 20 including theelectrode patterns 14 from the mother ceramic sheet 12. The stacking jig34 comprises a bottom wall, and a frame for peripherally enclosing theceramic sheets 35 which are stacked on the bottom wall.

As shown in FIG. 3, the stacking jigs 34 are placed on a conveyor 36. Aloading rack 37 is arranged on the upstream side of the conveyor 36 inorder to supply the stacking jigs 34 to the conveyor 36, while anunloading rack 38 is arranged on the downstream side of the conveyor 36in order to take the stacking jigs 34 out of the conveyor 36. FIG. 6also shows the conveyor 36, the loading rack 37 and the unloading rack38.

Referring to FIGS. 3 and 6, a plurality of vacant stacking jigs 34holding no ceramic sheets are placed on respective stages on the loadingrack 37. As shown by the arrow 39, the respective stages of the loadingrack 37 are displaced to be successively aligned with the upper surfaceof the conveyor 36. When a prescribed stage is aligned with the uppersurface of the conveyor 36, a piston of a cylinder 40 is driven alongthe arrow 41 to eject the vacant stacking jig 34 onto the conveyor 36.The stacking jig 34 thus placed on the conveyor 36 is carried by theconveyor 36 along the arrow 42, and carried toward a prescribed positionon the conveyor 36. At this prescribed position, the ceramic sheets 35are stacked on the stacking jig 34 as shown in FIG. 5.

After the ceramic sheets 35 are stacked on the stacking jig 34, theconveyor 36 is driven along the arrow 42, to carry the stacking jig 34to a position immediately ahead of the unloading rack 38. At thisposition, a vertical cylinder 45 is driven to move a push-in pawl 43along the arrow 44 while a horizontal cylinder 47 is driven to move thevertical cylinder 45 along the arrow 46. Thus, the stacking jig 34 ispushed onto a prescribed stage of the unloading rack 38. As shown by thearrow 48, the respective stages of the unloading rack 38 are displacedto be successively aligned with the upper surface of the conveyor 36.Thus, the unloading rack 38 is adapted to store a plurality of stackingjigs 34 that have received the stacked ceramic sheets 35. After theunloading rack 38 is filled up with the stacking jigs 34, it is detachedfrom the cutting/stacking device 22, so that the stacking jigs 34 arecarried to a next step, i.e., the pressing station 21 shown in FIG. 1,with the unloading rack 38.

Referring to FIG. 3, CCD cameras 49 and 50 are arranged above the sheetcutting stages 25, in order to detect the positions of the registrationmarks 15 which are provided on the mother ceramic sheet 12. In order topunch the regions 20 (FIG. 2) of the mother ceramic sheets 12 includingthe electrode patterns 14, a cutting head 52, whose periphery isenclosed with a cutting edge 51, is arranged in the vicinity of the CCDcameras 49 and 50.

According to this embodiment, the cutting head 52 and the CCD cameras 49and 50 are mounted on an XYθ robot 53, so that the same are movable indirections X, Y and θ. The cutting head 52 and the CCD cameras 49 and 50may alternatively be driven by separate driving systems.

FIGS. 7, 8 and 9 show the operations of the cutting head 52 and the CCDcameras 49 and 50.

As shown in FIG. 3, the mother ceramic sheets 12 are drawn out from theplurality of reels 23 onto related sheet cutting stages 25 and fixedthereto respectively. As hereinabove described, this operation isachieved by the structure shown in FIG. 4. FIG. 7 shows another view ofthe process at this stage.

As seen in FIG. 7, a prescribed one is selected from the plurality ofmother ceramic sheets 12, and the XYθ robot 53 is so driven that theregistration marks 15 provided on the selected mother ceramic sheet 12come into the visual fields of the CCD cameras 49 and 50. The CCDcameras 49 and 50 image-process the positions of the registration marks15. The results of such image processing are applied to a computer (notshown), which in turn calculates corrected values as to the positionswhere the mother ceramic sheet 12 should be punched.

Then, as shown in FIG. 8, the XYθ robot 53 is driven in response to theaforementioned corrected values, to move the cutting head 52 toward themother ceramic sheet 12. Thus, the regions 20 provided with theelectrode patterns 14 as shown in FIG. 2 are punched. The punchedceramic sheets, which are hidden by the cutting edge 51 and not shown inFIG. 8, are carried away from the cutting position by the cutting head52. In order to carry the punched ceramic sheets reliably, the cuttinghead 52 comprises a vacuum function device (not shown) for holding thepunched ceramic sheets by suction.

As shown in FIG. 9, the cutting head 52 is driven by the XYθ robot 53 tocarry the ceramic sheets to the stacking jig 34 which is placed on theconveyor 36, and stacks the ceramic sheets one upon the other on thestacking jig 34.

The aforementioned operations are repeated so that any arbitrary memberof ceramic sheets are stacked on the stacking jig 34 in arbitrary order.

In order to obtain a ceramic layered product for manufacturing amultilayer ceramic capacitor, it is necessary to also stack ceramicsheets which are provided with no electrode patterns. Therefore,preferably at least one of the reels 23 set on the reel stand 24, i.e.,a mother ceramic sheet 12(a) which is drawn out from a reel 23(a), isprovided with no electrode patterns, etc., as shown in FIG. 3. In thiscase, the mother ceramic sheet 12(a) may simply be drawn out at aconstant amount since it is not necessary to correctly position anyelectrode pattern on the mother ceramic sheet 12(a) before punching.

As hereinabove described, the prescribed ceramic sheets 35 which arestacked on the stacking jig 34 are subjected to hydrostatic pressing,for example, in the pressing station 21 shown in FIG. 1, and thereaftercut to obtain single chips for multilayer ceramic capacitors. Then eachchip is fired and provided with external electrodes, to obtain a desiredmultilayer ceramic capacitor.

In the aforementioned embodiment, the reels 23 are stored in containers,so that the mother ceramic sheets 12 can be easily stored so as toremain clean. However, if such an advantage is not desired, it is notnecessary to store the reels in containers.

The present invention is not restricted to manufacturing a ceramiclayered product for a multilayer ceramic capacitor, but is alsoapplicable to manufacturing layered products for other types ofmultilayer ceramic electronic components such as a multilayer inductor,a multilayer LC filter, a multilayer circuit board, or the like.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the scopeof the present invention being limited only by the terms of the appendedclaims.

What is claimed is:
 1. A method of manufacturing a ceramic laminacomprising the steps of:a) preparing a plurality of reels wound with arespective plurality of elongated mother ceramic sheets, each having aplurality of electrode patterns, and a plurality of registration marks,said registration marks having predetermined relative locations on saidsheets with respect to said electrode patterns, distributed along itslongitudinal direction; b) drawing out said mother ceramic sheets fromrespective ones of said plurality of reels onto corresponding sheetcutting stages; c) determining the location of a region including atleast one of said electrode patterns within one of said mother ceramicsheets on a selected said sheet cutting stage, on the basis of saidregistration marks, and punching out a first ceramic sheet correspondingto said region from said mother ceramic sheet employing a cutting headwhose periphery is enclosed with a cutting edge; and d) carrying saidfirst ceramic sheet punched out of said mother ceramic sheet to astacking jig employing said cutting head and stacking said first ceramicsheet on said stacking jig.
 2. A method of manufacturing a ceramiclamina in accordance with claim 1, wherein said step of preparing aplurality of reels comprises the step of storing a plurality of reelsand the step of selecting said ones of said stored plurality of reelsfrom which said mother ceramic sheets are drawn out.
 3. A method ofmanufacturing a ceramic lamina in accordance with claim 2, wherein saidstep of storing said plurality of reels comprises the step of storingsaid reels in containers.
 4. A method of manufacturing a ceramic laminain accordance with claim 1, wherein said mother ceramic sheets areintermittently drawn out in said step of drawing out said mother ceramicsheets from said reels, and said step of punching said one of saidmother ceramic sheets employing said cutting head is carried out whensaid mother ceramic sheet is in a stopped state.
 5. A method ofmanufacturing a ceramic lamina in accordance with claim 4, furthercomprising the step of cutting a scrap sheet resulting from said step ofpunching said one of said mother ceramic sheets employing said cuttinghead, for every intermittent step of drawing out said mother ceramicsheet.
 6. A method of manufacturing a ceramic lamina in accordance withclaim 1, further comprising the steps of:e) repeating said step (c) topunch out a second said ceramic sheet; and f) carrying said secondceramic sheet to said stacking jig and stacking said second ceramicsheet on said first ceramic sheet.
 7. A method of manufacturing aceramic lamina in accordance with claim 6, further comprising the stepof repeating said steps (a) and (f).
 8. A method of manufacturing aceramic lamina in accordance with claim 6, wherein said first and secondceramic sheets are punched from one said mother ceramic sheet.
 9. Amethod of manufacturing a ceramic lamina in accordance with claim 6,wherein said first and second ceramic sheets are punched from differentones of said mother ceramic sheets.
 10. A method of manufacturing aceramic lamina in accordance with claim 9, further comprising the stepof aligning said stacking jig with said respective different motherceramic sheets during said steps (d) and (f).
 11. A method ofmanufacturing a ceramic lamina in accordance with claim 1, furthercomprising the steps of:preparing an insulation reel wound with arespective elongated mother ceramic insulation sheet having no electrodepattern thereon; drawing out said mother ceramic insulation sheet fromsaid insulation reel onto a corresponding sheet cutting stage; punchingout an insulation ceramic sheet from said mother insulation ceramicsheet; and carrying said insulation ceramic sheet to said stacking jigand stacking it on said first ceramic sheet.